A THz smart switch based on a VO₂ metamaterial that switches between wide-angle ultra-wideband absorption and...

Terahertz (THz) devices are highly desired in modulation, detection, and receiving devices. Recently, active metamaterials have been applied as a novel strategy for the design of terahertz devices. However, their performance and function need to be further developed. Here, an active controllable THz smart switch is designed using vanadium dioxide (VO₂), a thermally controlled phase transition material. The THz smart switch is simple, consisting of three layers: the top and bottom layers are VO₂, and the intermediate dielectric layer is SiO₂. Based on impedance matching theory and an analysis of the electric field distribution, the mechanism by which the device achieves perfect absorption is studied. The results show that the THz smart switch can achieve ultra-wideband and wide-angle absorption and transmission of terahertz waves, and can flexibly switch between these modes. When VO₂ is in the metal state, the THz smart switch can achieve ultra-wideband absorption, and the absorption bandwidth is as high as 5.8 THz (A > 90%). When VO₂ is in the insulating state, the THz smart switch can achieve ultra-wideband transmission, with an average transmission of 86% (Δf = 4.7 THz). As the ambient temperature changes, the THz smart switch can achieve active switching of the absorption from 2% to 99.9% and the transmission from 89% to 0%. It is worth noting that the THz smart switch can also realize the active switching of absorption and transmission over a wide-angle range. This study provides important insights for the design of active controllable devices and also offers a new concept for the design of THz multi-functional devices.